Ali Ruqaya M, Alsudani Ahmed A
Veterinary Directorate, Baghdad, Iraq.
Directorate of Public Health, National Specialized Center for Chest and Respiratory Disease, Baghdad, Iraq.
Int J Mycobacteriol. 2016 Dec;5 Suppl 1:S193-S194. doi: 10.1016/j.ijmyco.2016.09.039. Epub 2016 Nov 11.
Early detection for tuberculosis (TB) and rifampicin-resistant TB (RRTB) is crucial for proper control of this disease. WHO recommended the use of the GeneXpert assay at district level to cover these two public health demands? A study evaluated the diagnostic impact of the GeneXpert assay in detecting TB and RRTB. Odd results were observed in this study in the form of discordance between the GeneXpert assay and the conventional culture and drug-susceptibility testing (DST).
To assess the molecular diagnostic validity of the GeneXpert assay when results do not match phenotypic results given by DST.
Pulmonary TB patients with recently detected sputum positive for acid-fast bacilli (AFB) were recruited from random geographical clusters (18 out of 36 primary healthcare districts in the middle five governorates in Iraq) during a 1-year period (November 2013-October 2014). Sputum samples from all enrolled patients were sent for GeneXpert assay testing, culture, and DST. Genotype mycobacterium (GM) from Hain Lifescience (Nehren, Germany) was used to detect non-tuberculosis mycobacteria (NTM) whenever suspected. Those with discordant results regarding the status of RRTB between GeneXpert assay and DST were retested with the line probe assay (LPA). Simple frequency distribution was used to describe study results.
Four-hundred ten patients were enrolled, all of whom were culture positive. Only two patients were found negative for TB on GeneXpert assay who were then diagnosed as NTM by LPA (GM). Out of the 408 patients, discordance between GeneXpert and DST regarding the status of rifampicin susceptibility was observed in 17 cases (4%). Nine patients were RR on GeneXpert but rifampicin susceptible (RS) on DST. LPA agreed with GeneXpert assay for all nine cases. Eight patients were RS on GeneXpert but RR on DST. Here, LPA disagreed with GeneXpert assay only in one patient who was found to be RR by LPA.
GeneXpert assay is a valid molecular test for TB and RRTB regardless of its discordance with conventional culture and DST.
结核病（TB）和耐利福平结核病（RRTB）的早期检测对于有效控制该疾病至关重要。世界卫生组织是否建议在地区层面使用GeneXpert检测来满足这两项公共卫生需求？一项研究评估了GeneXpert检测在检测结核病和耐利福平结核病方面的诊断影响。在这项研究中观察到了奇怪的结果，表现为GeneXpert检测与传统培养及药敏试验（DST）之间存在不一致。
当GeneXpert检测结果与DST给出的表型结果不匹配时，评估GeneXpert检测的分子诊断有效性。
在1年期间（2013年11月至2014年10月），从随机地理区域（伊拉克中部五个省份36个初级医疗保健区中的18个）招募最近痰涂片抗酸杆菌（AFB）阳性的肺结核患者。将所有入选患者的痰标本送去进行GeneXpert检测、培养和DST。每当怀疑有非结核分枝杆菌（NTM）时，使用德国海因生命科学公司（Nehren）的基因型分枝杆菌（GM）检测试剂盒检测NTM。对于GeneXpert检测和DST在耐利福平结核病状态方面结果不一致的患者，用线性探针分析（LPA）进行重新检测。使用简单频率分布来描述研究结果。
共纳入410例患者，所有患者培养均为阳性。GeneXpert检测发现仅2例患者结核病呈阴性，这2例患者随后经LPA（GM）诊断为NTM。在408例患者中，观察到17例（4%）GeneXpert检测和DST在利福平敏感性状态方面存在不一致。9例患者GeneXpert检测显示为耐利福平（RR），但DST显示对利福平敏感（RS）。9例患者的LPA结果与GeneXpert检测一致。8例患者GeneXpert检测显示为RS，但DST显示为RR。在此，LPA仅在1例患者中与GeneXpert检测结果不一致，该患者经LPA检测为RR。
无论GeneXpert检测与传统培养及DST是否存在不一致，它都是一种有效的结核病和耐利福平结核病分子检测方法。
